1. Technical Field
A first aspect of the present invention relates to a riding lawnmower vehicle including main drive wheels that can be driven by a traction power source and a lawnmower. A second aspect of the present invention relates to a riding lawnmower vehicle that includes a front frame supporting at least two front wheels, a rear frame supporting at least two rear wheels, a joint unit connecting the front frame and the rear frame which cooperatively constitute an articulated vehicle body, a steering apparatus changing a twist angle between the front frame and the rear frame according to an operation amount of an operation unit, and a lawnmower. A third aspect of the present invention relates to a riding lawnmower vehicle including drive wheels that can be driven by an electric motor and a lawnmower.
2. Related Art
Conventional lawnmower vehicles including lawnmower can generally be classified into two types: walk behind lawnmower vehicles that a user operates from the rear, and riding lawnmowers vehicle that a user rides and operates. A conventional riding lawnmower vehicle includes main drive wheels that can be driven by a traction power source and a lawnmower. A user riding on a vehicle of this type can maneuver the lawnmower to cut lawn grass at a predetermined height.
As discussed in U.S. Pat. Nos. 7,017,327 or 6,591,593, an electrically driven riding lawnmower vehicle, related to the first or third aspect of the present invention, includes an engine, a generator driven by the engine, and an electric traction motor. The electric energy generated by the generator can be supplied to the electric traction motor operable to drive the two rear wheels (U.S. Pat. No. 7,017,327) or two front wheels (U.S. Pat. No. 6,591,593). This type of riding lawnmower vehicle can be referred to as a hybrid-type riding lawnmower vehicle.
According to the riding lawnmower vehicle discussed in U.S. Pat. No. 6,591,593, related to the first aspect of the present invention, a lawnmower is provided forward of two front wheels and two rear wheels.
Furthermore, as discussed in International Patent Publication No. 2006/086412, a riding lawnmower vehicle relating to the first or third aspect of the present invention includes two front wheels, one caster wheel (rear wheel), a fuel cell, and an electric traction motor. The electric energy generated by the fuel cell can be supplied to the electric traction motor operable to drive the two front wheels. Furthermore, a riding lawnmower vehicle discussed in U.S. Pat. No. 3,732,671 includes two front wheels, two rear wheels, a battery, and an electric traction motor operable to drive the two rear wheels when electric energy is supplied to the electric traction motor from the battery.
According to the riding lawnmower vehicle described in U.S. Pat. No. 3,732,671, a transaxle is provided between two rear wheels.
Furthermore, a conventional riding lawnmower vehicle relating to the second aspect of the present invention includes a front frame supporting front wheels, a rear frame supporting rear wheels, and an articulated-type turning mechanism that connects the front frame and the rear frame via a joint unit so that the vehicle body can twist. When the riding lawnmower vehicle includes such an articulated-type turning mechanism, an appropriate steering apparatus is provided to change the twist angle between the front frame and the rear frame when a user operates a steering wheel or a comparable operation unit.
According to the riding lawnmower vehicle discussed in U.S. Pat. No. 6,591,593, a forward vehicle body and a rear vehicle body are connected via a joint unit including a hitch arm/ball arrangement. An operator can ride on the forward vehicle body, while an engine, a generator, and an inverter are mounted on the rear vehicle body. The forward (front) vehicle body supports motor driven wheels. The rear vehicle body supports caster wheels.
The conventional lawnmower vehicles discussed in U.S. Pat. Nos. 6,591,593, 7,017,327, International Patent Publication No. 2006/086412, and U.S. Pat. No. 3,732,671 are related to the second aspect of the invention.
In all of the riding lawnmower vehicles discussed in U.S. Pat. Nos. 7,017,327, 6,591,593, International Patent Publication No. 2006/086412, and U.S. Pat. No. 3,732,671, which relate to the first aspect of the present invention, there is room for improvement in the manner in which the finite space available on the lawnmower vehicle is used; that is, the efficiency of use of the space can be improved in each of these vehicles. According to riding lawnmower vehicle discussed in U.S. Pat. No. 7,017,327, an engine is mounted on the front side of a driver's seat and a battery is located near the driver's seat positioned next to an inverter. The battery is largely offset from the engine in the longitudinal direction of the vehicle. Therefore, room for improvement is available should it be found necessary to increase the efficiency of use of space in the riding lawnmower vehicle be necessary.
Furthermore, a mower driving motor is directly set up on the lawnmower. Although the mower driving motor has a flat, circular “pancake” shape, the relationship between the overall axial length and the outer diameter is not restricted. Therefore, there is sufficient room for improvement if it is required to widen the space between the lawnmower and the vehicle body frame. There is sufficient room for improvement if it is required to enhance the efficiency of use of a limited space. Additionally, the lower end of the engine is positioned higher than a rotation center axis of rear wheels (drive wheels). Not only is the position of the centroid (and of the center of mass) relatively high but also the lower space of the vehicle can be effectively used. There is sufficient room for improvement if it is required to enhance the degree of effectively using a limited space.
With the riding lawnmower vehicle discussed in U.S. Pat. No. 6,591,593, there is sufficient room for improvement in the efficiency of use of a limited space of the vehicle including a battery is available, because the installation location of the battery is not restricted. Furthermore, in the arrangement of the mower driving motor positioned above a lawnmower blade, there is no restriction applied to the relationship between the overall axial length and the outer diameter. Therefore, a margin for improvement is available if it is necessary to widen the space between the lawnmower and the vehicle body frame. There is also a margin for improvement in the efficiency of use of a limited space. Furthermore, the disclosure of that publication includes no disclosure regarding the positional relationship between the lower end of the engine and the rotation center axis of the drive wheels (front wheels). As such, it is possible that the lower space of the vehicle may not be effectively used and that, thus, a margin for improvement in the efficiency of use of a limited space is available, if required.
According to the riding lawnmower vehicle discussed in International Patent Publication No. 2006/086412, all of the battery, the fuel cell, and the mower driving motor are offset from the front wheels (drive wheels) in the longitudinal direction of the vehicle. Thus, further improvement in the efficiency of use of the finite space available is possible. Furthermore, the related-art mower driving motor is located outside a lawnmower reel in the width direction of the vehicle and there is no description concerning the relationship between the overall axial length and the outer diameter in the arrangement of the mower driving motor. Therefore, still further improvement in the efficiency of use of the finite space available is possible. Furthermore, as there is no description regarding the positional relationship between the lower end of the battery (or the fuel cell) and the rotation center axis of the front wheels (drive wheels), the lower space of the vehicle may not be effectively used. Thus, still further improvement in the efficiency of use of the finite space available is possible.
According to the riding lawnmower vehicle discussed in U.S. Pat. No. 3,732,671, although the battery overlaps the rear wheels (drive wheels) in the width direction of the vehicle, the two rear wheels cannot be independently driven. Because the transaxle extends between two rear wheels, a large portion of the battery cannot be overlapped with the rear wheels when viewed from the side (one end to the other end in the width direction) of the vehicle. As such, improvement in the efficiency of use of the finite space available is possible. Furthermore, the mower driving motor is positioned above the lawnmower blade and has a rotational shaft extending in the vertical direction, and the overall axial length of the mower driving motor is longer than the outer diameter. Therefore, still further improvement in the efficiency of use of the finite space available is possible.
Furthermore, because the lower end of the battery is positioned higher than the rotation center axis of the rear wheels (drive wheels), the lower space of the vehicle may not be effectively used. Thus, still further improvement in the efficiency of use of the finite space available is possible. As described above, in the structure of any one of the above-described conventional riding lawnmower vehicles, improvement in the efficiency of use of the finite space available is possible.
Improvement in the efficiency of use of the finite space available on the mower is also possible in connection with the conventional riding lawnmower vehicle that includes an articulated-type turning mechanism connecting a front frame and a rear frame so that the vehicle body can twist, which relates to the second aspect of the present invention. For example, in the conventional riding lawnmower vehicle, the configuration of the relationship between a grass-collecting duct connecting the lawnmower to a grass storage tank and a power transmission mechanism capable of transmitting the driving force of the mower driving motor to the lawnmower can be improved to enhance the efficiency of use of a limited space. Furthermore, it is also possible to improve the power by improving its fuel efficiency or making it possible to use more common parts or components.
U.S. Pat. No. 6,591,593 contains no disclosure of the articulated-type turning mechanism applicable to a riding lawnmower vehicle. Furthermore, according to the riding lawnmower vehicle discussed in U.S. Pat. No. 6,591,593, improvement in the efficiency of use of the limited space is possible. Furthermore, there is room for improvement in use of common parts or components. As described above, the configuration of the riding lawnmower vehicle discussed in U.S. Pat. No. 6,591,593 can be significantly improved. The riding lawnmower vehicle discussed in any one of U.S. Pat. No. 7,017,327, International Patent Publication No. 2006/086412, and U.S. Pat. No. 3,732,671 does not include any articulated-type turning mechanism.
According to the above-described conventional riding lawnmower vehicle relating to the third aspect of the present invention, there is sufficient room for improvement in the cooling system for an electric motor. For example, the above-described conventional riding lawnmower vehicles may include various electric motors, such as electric motor operable to drive a wheel, electric motor operable to steer a caster wheel, and electric motor operable to drive a lawnmower. To assure sufficient performance, it is desired to appropriately cool respective electric motors because temperature of the electric motors are inclined to rise when they are used. In this respect, according to the above-described conventional riding lawnmower vehicles, there is sufficient room for improvement if it is required to cool the electric motor. If the riding lawnmower vehicle includes a control circuit unit and an inverter to drive an electric motor, there is sufficient room for improvement if it is required to cool the control circuit unit and the inverter. Furthermore, if the riding lawnmower vehicle includes a coolant piping in which coolant flows to cool an electric motor, there is sufficient room for improvement in the coolant piping.